132 
ACTINOPTEEYGII. 
only exposed on the cheek in its lower portion. The suboperculnm 
exhibits a feeble ascending process at its antero-superior angle; 
and the interoperculum is relatively large. There are about six 
broad hranchiostegal rays; and a large broadly-oval gnlar plate, 
marked by a V-shaped groove for the sensory canal, occurs in front, 
In the axial skeleton of the trunk the notochord must have been 
persistent, and no traces of ossifications in its sheath have been 
detected. The neural and haemal arches, however, are all well 
ossified at least superficially, and only the thickness of the squa- 
mation prevents their being frequently displayed. Throughout the 
trunk as far as the middle of the caudal region, the neural spines 
are not fused with their corresponding arches, this fusion taking 
place only in the hinder half of the tail. The first few neurals are 
especially robust, expanded at their upper end, though not sup¬ 
porting the stout ridge-scales, and directly apposed to their arches; 
the remaining neurals are more slender, taper below, and slightly 
overlap their arches. The ribs in the abdominal region form a regular 
series, but do not reach the ventral border; the hsemal spines 
in the caudal region are fused with their corresponding arches, are 
sharply bent backwards, and exhibit a small triangular expansion 
anteriorly at their base. There are no intermuscular bones. 
All the fins bear uniserial fulcra of moderate size; but the two 
halves of the fin-rays at least in the median fins seem to be loosely 
apposed. The number of the fin-supports in the dorsal is proved to 
equal exactly that of the rays, and there is no fusion of supports at 
its origin. The paired fins are small and delicate, but nothing 
worthy of note is known in reference to the supports. There is a 
large post-temporal plate on each side articulated with the supra- 
clavicle; and the long, arched clavicle exhibits its anterior margin 
sharply bent inwards. 
The scales in Dcipedius have a broad peg-and-socket articulation, 
but no sharply thickened rib on the inner face. The azygous ridge- 
scale are not acuminate, except at the origin of the anal fin, where 
a few are enlarged. 
Most of the minor characters of Dapedius are very variable, and 
it is thus difficult to subdivide the genus into well-defined species. 
In the majority of forms, the scales are tuberculated only in the 
anterior dorsal and ventral regions ; rarely the tuberculations extend 
over the flank. One group of species has the marginal teeth bi¬ 
cuspid, while another group has the same teeth unicuspid; but in 
observing this character it must be remembered that the former 
teeth when seen in side view may easily be mistaken for the latter. 
There are also tolerably constant differences in the form of the trunk, 
